Known as one of techniques for directly producing a strip from molten metal is twin-roll continuous casting in which molten metal is supplied to between a pair of rotated rolls so as to deliver solidified metal in the form of strip.
FIGS. 1-3 show an example of a conventional twin-roll casting machine with a pair of chilled rolls 1a and 1b horizontally juxtaposed and a pair of side weirs 2a and 2b associated with the rolls 1a and 1b. 
The rolls 1a and 1b are constructed such that cooling water passes through insides of the rolls, a nip G between the rolls being controllable to be increased or decreased depending upon thickness of a strip 3 to be produced.
Velocity and direction of rotation of the rolls 1a and 1b are set such that the outer peripheries of the respective rolls move from above towards the nip G at the same velocity.
The one and the other side weirs 2a and 2b surface-contact one and the other ends of the rolls 1a and 1b, respectively. Nozzle pieces 4a and 4b for supply of molten metal are arranged in a space defined by the rolls 1a and 1b and side weirs 2a and 2b so as to be positioned just above the nip G (see, for example, Patent Literature 1).
The one and the other nozzle pieces 4a and 4b are supported to have a constant gap against the one and the other side weirs 2a and 2b, respectively.
Each of the nozzle pieces 4a and 4b has a top with an elongated nozzle trough 6 for reception of molten metal 5, and longitudinal side walls each with a plurality of openings 7 at portions of the walls adjacent to lower ends of the walls so as to supply the molten metal 5 from the nozzle trough 6 to between the rolls 1a and 1b, the openings 7 being spaced apart from each other axially of the roll 1a, 1b. Pouring of the molten metal 5 into the respective nozzle troughs 6 provides a molten metal pool 8 above the nip G and in contact with outer peripheries of the rolls 1a and 1b. 
As shown by arrows in FIG. 2(a), with respect to each of the nozzle pieces 4a and 4b, the openings 7 are formed symmetrically at the portions adjacent to the one and the other rolls 1a and 1b, respectively.
In the above-mentioned twin-roll casting machine, the molten metal pool 8 is formed and the rolls 1a and 1b are rotated with the cooling water passing through and cooling the rolls 1a and 1b, so that molten metal 5 is solidified on the outer peripheries of the rolls 1a and 1b into solidified shells 9 so as to deliver downward the strip 3 from the nip G.
In this case, loads are applied to necks of the respective rolls 1a and 1b in directions toward each other so as to make the produced strip 3 to have a targeted thickness.    [Patent Literature 1] JP 2000-202590A